MM951

I bought used MAF chips and stuck them in my DME...
Does bucking under load and hot exhaust indicate the car is running too rich? My narrowband AF is showing the first blue light when this happens...

DDP

Don't take this the wrong way, but how many issues have you had that could easily be solved with a wideband so you KNOW where you're at and a GOOD set of chips?

I can't say I've ever felt the muffler tip, but a hot exhaust means high EGTs which means lean, not rich. Bucking could be overly lean or overly rich. Or a bunch of other problems, lol.

You need to go back to the basics. Get a known good set of chips for you MAF, injectors and also a good wideband so you know what's going on. Make sure you have no intake or exhaust leaks. Make sure all your sensors (TPS/MAF/etc.) are good. Then the car will run rock solid.

Why not put in all the factory stuff with factory chips, get it running good. Then put on the MAF and correct chips, etc? You need to rule some things out here. And with your narrowband you're running near blind.

Spend some money to save some money. Experience talking here, not V2Rocket.

Chris White

Yes and no….running lean will raise your EGT but so will running very rich. The additional fuel is burnt in the exhaust system. If the exhaust tip is hot I would vote for overly rich. Typically a 951 will start bucking when you get it really really rich (like 10:1 or less)
The narrow band sensor is hopeless in this range – and if the EGTs go up it will get worse.
Sounds like you need some better analyses tools and some known chips!

DDP

Good point, Chris.

Is it backfiring, though? Popping?

Duke

The exhaust tip always get hot. Even if you running super low EGT that still means 700+ celcius.

Keithr726

My tip is burning to the touch. I'm only running 11 or so PSI right now and on boost my AFR is 11.5 and 14.7 at idle.

MM951

DDP- I understand you, but I don't have any of the factory parts (AFM, chips, turbo, etc) I bought the car with all of these mods. I don't have a WB02 yet, but it will be my next purchase as soon as I get my maxtronic. I was couting on buying a friends LC-1 w/ gauge for $110, but he hasn't gotten it to me yet.

All my sensors are good, only problem electrical problem I thought I had was a failed DME.. Turns out what I needed was to replace the reference sensor harness as it was slightly cracked under the boot.


I got a set of used Huntly Racing chips off of ebay that match my " Huntley Racing Stage 3" MAF and an "upgraded turbo".

The exhaust is no longer very hot after adjusting the ARC-2 ( -1 click on the low, -1 mid , +2 on the accel) I have a nice idle and now it runs smoothly (I haven't gone past 4,000 rpm , minus the one time I got a lot of wheel spin and hit 6K briefly) and revs pretty cleanly/smooth. It only seems to buck slightly at 2,000-2,500 rpm in the higher gears.

I have 18" of vac on cold start up, ~20-21 vac warm idle, 26-28" vac on decel. There are no intake or exhaust leaks at all. All new couplers/clamps/hoses. The exhaust has no leaks anywhere.. I have gone as far as 10psi (10psi just before 3K rpm in 3rd gear and I let off by 4K rpm) Oh and the injector duty cycle gauge hasn't gotten fast 50% yet.

Thanks guys

EDIT: At one point it did backfire and had a sharp "crack" when I cut the throttle. This was right after I put the new chips in and didn't adjust the ARC-2. I didn't drive or anything , just a rev to 3K in neutral. After I got rid of that was when I experienced the bucking

DDP

I have an extra AFM and stock chips. I would happily send them to you if you paid for shipped, to borrow and ship back after you figure out the issues. The only problem comes in do you have stock injectors? Your turbo isn't stock, either. You really just need to get the correct chip burnt. If you're interested in my stock parts, PM me. Either way, good luck.

billthe3

Chris White

Hmmm....Huntley stage 3....do a search - that set up has a long history of bucking at low load, low rpm. Most folks ended up tossing it out.

MM951

I was searching all night.. I am bit a disappointed that its such a problem with these MAFs. From what I understand, "clocking" it could help as well as placing it has far as possible from the turbo. I'll give that a shot and see how it is


The car does not cut out and seems to run very well under boost.. just the low rpm crusing makes it nearly impossible to drive. On cold startup (~30*F) the problem is worse..

Would it be a bad idea to buy a new "smaller" MAF from pro-flow or a Mustang 5.0/ 4.6 MAF? I've read about the Bosch HMF5 MAF working wll on other Motronic cars (turbo 5 cyl volvos etc) - any thoughts?

I was also reading up on the FQS switch.. I was thinking of putting it on the setting that retards the timing for a little added safety. From what I understand it is "safer" but makes it weaker off boost (doesn't bother me right now) If the car is running pretty good on boost should I just leave it alone?

I'll report back later today... thanks for the help

fast951

You are using a MAF with a AFM chip! The supposedly MAF chip you have is a AFM chip.
You are attempting to convert the MAF signal to look like the AFM signal so the DME understands it. This approach has way too many flaws, but we'll leave this for another discussion (search is your friend on this subject). If you have a WB sensor, you can fine tune the AFR enough to be ok. Changes in temps, boost or ... and you have to retune again. Of course, at PT your ignition can be off and there is nothing you can do about it except to use a TRUE MAF chips. Two MAF sensors can look 100% identical, yet they can generate a totally different output curve based on their calibration. Unless someone knows the calibration of "your" MAF, a true MAF chip cannot be developed. The problem you are facing is not a bad MAF sensor, the problem remians in the MAF conversion (MAF to AFM).. So changing sensors does not help much, the basics remain the same.

EGTs can be affected by AFR as well as ignition timing. Popping in the intake means lean, backfiring from the exhaust is a indication of a rich condition.

Take a step back, figure out your long term goal and fix it correctly the first time. Much less expensive than the second time.

MM951

Hey John, you were right (of course ) I just read that the HR chips are really autothority stage 2 AFM chips. I'm a bit peeved they were advertised as MAF chips but at least they were only $40

I understand you and I don't think I will be driving the car anymore until I have proper MAF chips. Do you think its likely I caused damage by driving it yesterday? Whenever I did go into the boost it was for less then 2 seconds each time and I let off by 4K rpm. It did build to just past 15psi VERY quickly but I let off right away.

Long term goal is ~330 reliable rwhp. Proper chips, WB02, and a better piggyback seem to be the way to go?

ehall

+1 on the V2rocket crack! ROFL

Keithr726

The scivision MAF kit uses a HMF5.